Non-volatile memory device, methods of fabricating and operating the same

ABSTRACT

A non-volatile memory device includes a floating gate formed on a substrate with a gate insulation layer interposed therebetween, a tunnel insulation layer formed on the floating gate, a select gate electrode inducing charge introduction through the gate insulation layer, and a control gate electrode inducing charge tunneling occurring through the tunnel insulation layer. The select gate electrode is insulated from the control gate electrode. According to the non-volatile memory device, a select gate electrode and a control gate electrode are formed on a floating gate, and thus a voltage is applied to the respective gate electrodes to write and erase data.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/364,570 filed Feb. 3, 2009, which is a divisional of U.S. patentapplication Ser. No. 11/323,355, filed on Dec. 30, 2005, now U.S. Pat.No. 7,492,002 issued Feb. 17, 2009, which in turn claims priority under35 U.S.C. §119 to Korean Patent Application No. 2004-116845, filed onDec. 30, 2004 in the Korean Intellectual Property Office, thedisclosures of which are each incorporated by reference herein in theirentireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device and to methodsof operating and fabricating the same. More specifically, the presentinvention is directed to a non-volatile memory device and to methods ofoperating and fabricating the same.

2. Description of Related Art

Non-volatile memory devices store data in an electrically insulatedmanner. Typically, non-volatile memory devices include stack-gate memorydevices, split-gate memory devices, and Electrically ErasableProgrammable Read Only Memory (EEPROMs) devices.

FIG. 1 is an equivalent circuit diagram of a cell array of aconventional split-gate memory device, and FIG. 2 is a cross-sectionalview of a conventional split-gate memory device.

FIG. 1 and FIG. 2, illustrate a cell array of a conventional split-gatememory device which adopts an NOR type cell array to randomly accessmemory cells. Memory cells are arranged in row and column directions toshare a source region 22 or a drain region 24 with adjacent memorycells. Each of the memory cells includes a channel region definedbetween a source region 22 and a drain region 24, a gate insulationlayer 12 formed on the channel region, a floating gate 14 formed on thegate insulation layer 12, a control gate electrode 16 formed on the gateinsulation layer 12 and the floating gate 14, and a tunnel insulationlayer 20 interposed between the control gate electrode 16 and thefloating gate 14. An insulation layer having an elliptical section isformed on the floating gate 14, so that a tip is formed to enhance atunneling efficiency.

As illustrated in FIG. 1, control gate electrodes 16 of memory cellsarranged in a column direction are connected to constitute a wordlineWLn, and source regions are connected to constitute a common source lineCSL. A drain region of memory cells arranged in a column direction isconnected to a bitline BLn. A NOR-type cell array of a stack-gate memorydevice has an over-erase problem, while a NOR-type cell array of asplit-gate memory device does not have an over-erase problem because thecontrol gate electrode formed on the gate insulation layer correspondsto a gate electrode of a select transistor.

In a split-gate memory device, a control gate voltage 16 is applied to acontrol gate electrode 16 for forming a channel below the control gateelectrode 16 and a program voltage of about 10 volts is applied to asource region 22 to inject charges into a floating gate 14 through agate insulation layer 12. The program voltage is coupled to the floatinggate 14 by an overlap capacitance of a source region 22 and the floatinggate 14. Thus, a high program voltage is required for inducing asufficient vertical field to a channel region. For this reason, thesource region 22 must be configured to have a high junction breakdownvoltage.

Unlike a split-gate memory device, an EEPROM is not required for ajunction structure for applying a high junction breakdown voltagebecause a relatively lower voltage is applied to a source region or adrain region.

FIG. 3 is an equivalent circuit diagram of a cell array of aconventional EEPROM, and FIG. 4 is a cross-sectional view of theconventional EEPROM.

Referring to FIG. 3 and FIG. 4, unlike a split-gate memory device, anEEPROM has a configuration where a select gate electrode and a controlgate electrode are isolated from each other. Memory cells of the EEPROMare arranged in row and column directions and share a source region 68and a drain region 66 with adjacent memory cells. Each of the memorycells includes a channel region defined between a source region 68 and adrain region 66, a tunnel insulation layer 68 and a gate insulationlayer 54 which are formed on the channel region, a floating gate 56formed on the tunnel insulation layer 52 and the gate insulation layer54, and a control gate electrode 60 formed on the gate insulation layer54 to be spaced apart from the floating gate electrode 56. A select gateelectrode 58 is formed on the floating gate 56 with an intergatedielectric 62 interposed therebetween. A floating diffusion layer 64 isformed in a substrate between the floating gate 56 and the control gateelectrode 60 to extend to the bottom of the tunnel insulation layer 52.

As illustrated in FIG. 3, select gate electrodes of memory cellsarranged in a column direction are connected to constitute a sensingline SL. Control gate electrodes of memory cells arranged in a columndirection are connected to constitute a wordline WL, and source regionsin a column direction connected to a common source line CSL. A sensingline SL is divided into a plurality of cell units to selectively erasememory cells connected to a wordline WL. Since an EEPROM requires awider cell area than a split-gate memory device, there is a limit to anintegration density of the EEPROM.

As previously stated, a split-gate memory device has a control gateelectrode acting as a gate electrode of a select transistor. Thus, thesplit-gate memory device is advantageous in high integration density.However, with split-gate memory devices, a high breakdown voltage isrequired because a program operation is performed by source junctioncoupling of a low coupling ratio. Meanwhile, an EEPROM device, in whicha program operation is performed by gate coupling, does not require ahigh junction breakdown voltage. Nevertheless, EEPROM devices havecertain disadvantages such as a large cell area and a limitedintegration density because a select gate electrode and a control gateelectrode are spaced apart from each other.

SUMMARY OF THE INVENTION

Exemplary embodiments of the present invention are directed to anon-volatile memory device which overcomes disadvantages of split-gatememory devices and EEPROMs and a method of operating and fabricating thenon-volatile memory device.

Further, exemplary embodiments of the present invention are directed toa non-volatile memory device in which a unit cell area is small and ahigh voltage is not applied to a source region or a drain region.

In an exemplary embodiment of the present invention, there is providedan non-volatile memory device including a floating gate formed on asubstrate with a gate insulation layer interposed therebetween, a tunnelinsulation layer formed on the floating gate, a select gate electrodeinducing charge introduction through the gate insulation layer, and acontrol gate electrode inducing charge tunneling occurring through thetunnel insulation layer.

In another exemplary embodiment of the present invention, there isprovided a non-volatile memory device including a source region and adrain region defining a channel region in a substrate, a gate insulationlayer formed on the channel region, a floating gate formed over the gateinsulation layer, a select gate electrode formed on the gate insulationlayer and the floating gate, a control gate electrode on a sidewall ofthe floating gate and the gate insulation layer to be opposite to theselect gate electrode. The non-volatile memory device further includesan intergate dielectric interposed between the select gate electrode andthe floating gate, and a tunnel insulation layer interposed between thecontrol gate electrode and the floating gate.

In another exemplary embodiment of the present invention, there isprovided a non-volatile memory device including a device isolation layerformed to define a plurality of active regions on a semiconductorsubstrate; a gate insulation layer formed on the respective activeregions, a floating gate formed on the respective gate insulationlayers, a sensing line formed on the gate insulation layer and thefloating gate to cross over the active regions and a wordline formed ona sidewall of the floating gate and the gate insulation layer to crossover the active regions. The wordline being opposite to the sensingline. The non-volatile memory device further includes an intergatedielectric interposed between the sensing line and the floating gate, anintergate dielectric interposed between the sensing line and thefloating gate, and a tunnel insulation layer interposed between thewordline and the floating gate.

In another exemplary embodiment of the present invention, there isprovided a method for operating a non-volatile memory device including asource region and a drain region defining a channel region, a gateinsulation layer on the channel region, a floating gate on the gateinsulation layer, a select gate electrode on the gate insulation layerand the floating gate, a control gate electrode on a sidewall of thefloating gate and the gate insulation layer to be opposite to the selectgate electrode, an intergate dielectric interposed between the selectgate electrode and the floating gate, and a tunnel insulation layerinterposed between the control gate electrode and the floating gate. Themethod includes a write step in which charges are injected to thefloating gate through the gate insulation layer, a read step in whichfluctuation of a threshold voltage of channel region below the floatinggate, which is caused by charges stored in the floating gate, is sensed,and an erase step in which tunneling of the charges stored in thefloating gate is induced through the tunnel insulation layer.

In another exemplary embodiment of the present invention, there isprovided a method for fabricating a semiconductor device. The methodincludes defining an active region on a semiconductor substrate, forminga floating gate conductive layer on an entire surface of the substratewith a gate insulation layer interposed between the active region andthe floating gate conductive layer, forming a top select gate electrodeon the floating gate conductive layer to cross over the active region;patterning the floating gate conductive layer to form a floating gate onthe active region, forming a tunnel insulation layer on a sidewall ofthe floating gate, and forming a sidewall select gate electrode and acontrol gate electrode on a tunnel insulation layer and a gateinsulation layer disposed at opposite sides adjacent to the floatinggate. The sidewall select gate electrode and the control gate electrodebeing opposite to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an equivalent circuit diagram of a cell array of aconventional split-gate memory device.

FIG. 2 is a cross-sectional view of a conventional split-gate memorydevice.

FIG. 3 is an equivalent circuit diagram of a cell array of aconventional EEPROM.

FIG. 4 is a cross-sectional view of the conventional EEPROM.

FIG. 5 is a symbolic diagram of a non-volatile memory device accordingto an exemplary embodiment of the present invention.

FIG. 6 is a top plan view of a non-volatile memory device according toan exemplary embodiment of the present invention.

FIG. 7 is a cross-sectional view taken along a line I-I′ of FIG. 5.

FIG. 8 is an equivalent circuit diagram of a cell array of anon-volatile memory device according to an exemplary embodiment of thepresent invention.

FIG. 9A through FIG. 17A are top plan views for explaining a method forfabricating a non-volatile memory device according to an exemplaryembodiment of the present invention.

FIG. 9B through FIG. 17B are cross-sectional views taken along linesII-II′ of FIG. 9A through FIG. 17A, respectively.

FIG. 9C through FIG. 17C are cross-sectional views taken along lines ofFIG. 9A through FIG. 17A, respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The exemplary embodiments of the present invention will now be describedmore fully hereinafter with reference to the accompanying drawings, inwhich preferred embodiments of the invention are shown. The inventionmay, however, be embodied in different forms and should not be construedas limited to the embodiments set forth herein. In the drawings, theheight of layers and regions are exaggerated for clarity. It will alsobe understood that when a layer is referred to as being “on” anotherlayer or substrate, it can be directly on the other layer or substrate,or intervening layers may also be present. Like numbers refer to likeelements throughout.

FIG. 5 is a symbolic diagram of a unit cell of a non-volatile memorydevice according to an exemplary embodiment of the present invention.The non-volatile memory device includes a source region S and a drainregion D defining an a channel region, a floating gate FG disposed overthe channel region, a select gate electrode SG and a control gateelectrode CG disposed on the floating gate FG. The control gateelectrode CG and the select gate electrode SG are oppositely insulatedfrom each other. A gate insulation layer is interposed between thefloating gate FG and the channel region, and a tunnel insulation layeris interposed between the control gate electrode CG and the floatinggate FG. Further, an intergate dielectric is interposed between theselect gate electrode SG and the floating gate FG. The select gateelectrode SG couples a program voltage to the floating gate FG, allowingcharges to be injected into the floating gate FG through a gateinsulation layer. An erase voltage is applied to the control gateelectrode CG to induce tunneling of charges through the tunnelinsulation layer. A capacitance C_(d) of a capacitor including theselect gate electrode SG, the floating gate FG, and the intergatedielectric is made higher than a capacitance C_(t) of a capacitorincluding the control gate electrode CG, the floating gate FG, and thetunnel insulation layer, enhancing program and erase efficiencies. Forexample, the intergate dielectric interposed between the select gateelectrode SG and the floating gate FG may be formed to have a largerarea than the tunnel insulation layer interposed between the controlgate electrode CG and the floating gate FG or the intergate dielectricmay include a material having a higher dielectric constant than thetunnel insulation layer.

In the non-volatile memory device, data is stored in the floating gateFG through the gate insulation layer by hot carrier injection. Thestored data is erased by Fowler-Nordheim tunneling (FN tunneling). Aprogram voltage applied to the select gate electrode SG is coupled tothe floating gate FG simultaneously to formation of a channel at achannel region formed therebelow. Hot carriers generated below thefloating gate FG around a boundary portion of the channel and the selectgate electrode SG are injected to the floating gate FG by a verticalfield crossing the gate insulation layer. If an erase voltage is appliedto the control gate electrode CG, charges are tunneled through thetunnel insulation layer by FN tunneling to erase the data stored in thefloating gate FG.

A program voltage is applied to a select gate electrode SG to be coupledto a floating gate FG, and a turn-on voltage is applied to a controlgate electrode CG to invert a channel region below a control gateelectrode. The turn-on voltage applied to the control gate electrode CGis higher than a threshold voltage at which the channel region isinverted. A ground voltage is applied to a drain region D and a constantvoltage is applied to a source region S, so that hot carriers generatedfrom a channel region are led to a vertical field by a voltage coupledto the floating gate to be stored in the floating gate over a potentialwall. If a typical Negative-Channel Metal Oxide Semiconductor (NMOS)transistor structure is adopted, electrons accelerated toward the sourceregion are to be stored in a floating gate over a potential wall of agate insulation layer.

Charges (generally, electrons) stored in the floating gate FG fluctuatea threshold voltage at which a channel region below the floating gate FGis inverted. A programmed threshold voltage that is a threshold voltagelaid in a state where electrons are accumulated in the floating gate FGis higher than an erased threshold voltage that is a threshold voltagelaid in a state where electrons are not accumulated therein. In thisregard, a voltage between a programmed threshold voltage and an erasedthreshold voltage is applied to read data stored in a floating gate. Forexample, if a read voltage is applied to the select gate electrode SGand/or the control gate electrode CG, a channel region below the selectgate electrode and the control gate electrode is inverted and a readvoltage is coupled to the floating gate. Inversion of the channel regionbelow the floating gate is determined depending on whether electrons arestored in the floating gate.

A ground voltage is applied to the source region S, the drain region D,and the select gate electrode SG and an erase voltage is applied to thecontrol gate electrode CG, erasing the data stored in the floating gateFG. The erase voltage applied to the control gate CG establishes a highelectric field at the tunnel insulation layer to lead to FN tunneling ofelectrons stored in the floating gate FG or holes supplied to thecontrol gate electrode.

A table [TABLE 1] shows an operating voltage of the non-volatile memorydevice according to an exemplary embodiment of the present invention. Inthe table [TABLE 1], Vs1, Vw1, Vs, and Vb1 denote a voltage applied to aselect gate electrode, a voltage applied to a control gate, a voltageapplied to a source region, and a voltage applied to a drain region,respectively.

TABLE 1 Vsl Vwl Vs Vbl program 8~10 V         2 V 3.3 V   0 V read 1 V1.5~2.0 V 0 V 1 V erase 0 V   10~12 V 0 V 0 V

The table [TABLE 1] is merely based on an exemplary embodiment of anoperation voltage of the non-volatile memory device according to thepresent invention, and thus applied voltages may vary with structuralcharacteristics of a device.

FIG. 6 is a top plan view of a unit cell of a non-volatile memory deviceaccording to an embodiment of the present invention, and FIG. 7 is across-sectional view taken along a line I-I′ of FIG. 6.

Referring to FIG. 6 and FIG. 7, the non-volatile memory device includesa source region 128 and a drain region 130 defining a channel region 103in a semiconductor substrate 100 and a gate structure. The gatestructure includes a floating gate formed on a gate insulation layer, aselect gate electrode on the floating gate with an intergate dielectricinterposed therebetween, and a control gate electrode formed on thefloating gate with a tunnel insulation layer interposed therebetween. Acapacitance C_(d) of a capacitor including the control gate electrode,the floating gate, and the tunnel insulation layer is preferably higherthan a capacitance C_(t) of a capacitor including the control gateelectrode, the floating gate, and the tunnel insulation layer, aspreviously described in FIG. 5. For this reason, an opposite area of theselect gate electrode and the floating gage is larger than that of thecontrol gate electrode and the floating gate. Alternatively, theintergate dielectric includes a material having a higher dielectricconstant than the tunnel insulation layer.

Specifically, a gate insulation layer 102 is formed on the channelregion 103. The floating gate 104 a is formed on the gate insulationlayer 102. The select gate electrode includes a sidewall select gateelectrode 126 a formed on one sidewall of the floating gate 104 a and onthe gate insulation layer and a top select gate electrode 120 formedover the floating gate 104 a. The control gate electrode 126 b is formedon the other sidewall of the floating gate 104 a and the gate insulationlayer 102. The sidewall select gate electrode 126 a and the control gateelectrode 126 b are symmetrical with each other. A spacer insulationlayer 116 a is interposed between the top select gate electrode 120 andthe sidewall select gate electrode 126 a and between the top select gateelectrode 120 and the control gate electrode 126 b. The spacerinsulation pattern 116 a insulates the top select gate electrode 120from the sidewall select gate electrode 126 a and the control gateelectrode 126 b. However, the top select gate electrode 120 and thesidewall select gate electrode 126 a are commonly connected to aninterconnection, so that an equivalent bias voltage Vs1 may be appliedthereto.

Insulation layers 114 a and 124 a, interposed between the control gateelectrode 126 b and the floating gate 104 a constitute a tunnelinsulation layer 125 a. Moreover, insulation layers 114 b, 115, 118, and124 b interposed between the select gate electrode 126 a and 120 b andthe floating gate 104 a constitute an intergate dielectric 125 b. Theinsulation layer formed on the spacer insulation pattern 116 a and thefloating gate 104 a may be a dielectric layer including a materialhaving a higher dielectric constant than the tunnel insulation layer 125a. For example, if the tunnel insulation layer 125 a is made of siliconoxide, the dielectric layer 118 may be made of at least one ofinsulative metal oxide and silicon nitride having a higher dielectricconstant than silicon oxide. As illustrated, since the non-volatilememory device has a symmetric structure, an insulation layer interposedbetween the sidewall select gate electrode 126 a and the floating gate104 a may be identical to the insulation layer constituting the tunnelinsulation layer 125 a.

The floating gate 104 a may have a tip 104 t disposed toward the controlgate electrode 126 b. Thus, an electric field is concentrated around thetip 104 t at an erase operation, so that charge tunneling based on FNtunneling has a high probability around the tip 104 t of the tunnelinsulation layer. A low capacitance C_(t) between the control gateelectrode 126 b and the floating gate 104 a may increase a difference ofvoltages applied to the tunnel insulation layer 125 a to induce FNtunneling at a relatively lower voltage. Since a capacitance between thefloating gate 104 a and the channel region 103 as well as a capacitancebetween the floating gate 104 a and the select gate electrode increasesa ratio of voltages coupled between the control gate electrode 126 b andthe floating gate 104 a, an erase efficiency may be enhanced.

As illustrated, the memory device may have a symmetrical sectionstructure. Thus, the floating gate 104 a may have a tip disposed towardthe sidewall select gate electrode 126 a. However, although a highvoltage is applied to a select gate electrode including a sidewallselect gate electrode 126 a and a top select gate electrode 120 at aprogram operation, a high capacitance C_(d) between the select gateelectrode and the floating gate decreases a difference of voltagesapplied to the intergate dielectric 125 b. Therefore, a probability ofFN tunneling occurring through an intergate dielectric is low and arelatively lower voltage is required. For this reason, FN tunneling doesnot occur substantially around a tip disposed toward the sidewall selectgate electrode 126 a.

A channel region 103 of the memory device may be divided into a regionbelow the sidewall select gate electrode 126 a, a region below thefloating gate 104, and a region below the control gate electrode 126 b.As previously stated, the divided channel region 103 is selectivelyturned on or off at program, read, and erase operations to store, read,and erase data.

FIG. 8 is an equivalent circuit diagram of an array of a non-volatilememory device according to an exemplary embodiment of the presentinvention. The non-volatile memory device includes a plurality of unitmemory cells arranged in row and column directions. The memory cellsshares a source region S and a drain region D with adjacent memorycells, respectively. Therefore, adjacent memory cells are symmetricallydisposed in a row direction. The unit memory cells include a floatinggate on a channel region defined between a source region S and a drainregion D and a select gate electrode and a control gate electrode whichare oppositely formed on the floating gate. Source regions S of the unitmemory cells are connected in a column direction to constitute a commonsource region CSL. A select gate electrode and control gate electrodesof the unit memory cells are connected in a column direction toconstitute a sensing line SL and a wordline WL, respectively. Thesensing line SL is divided at the respective memory cells to be oppositeto one wordline WL and a plurality of sensing lines SL. Drain regionsdisposed in a row direction are connected to a bitline.

The above-described cell array configuration allows for the selectiveerasure of memory cells sharing a sensing line SL. The memory deviceincluding the cell array is operated by selecting each unit cell towrite and read data and by selecting predetermined unit cells to erasethe data.

A constant voltage Vcc, a ground voltage GND, a write voltage, and aturn-on voltage are applied to a common source line CSL1, a selectbitline BL1, a select sensing line SL1, and a select wordline WL1 whichare connected to a selected memory cell CP, respectively. A groundvoltage is applied to an unselect common source line, an unselectbitline, an unselect sensing line, and an unselect wordline,respectively. By dong so, data is stored in a select memory cell.

Stored data may be read by selecting a specific memory cell. A groundvoltage, a read voltage, a turn-on voltage, and a verify voltage areapplied to a select common source line CSL1, a select bitline BL1, aselect sensing line SL1, and a select wordline WL1 which are connectedto a memory cell CP selected in a read operation, respectively. A groundvoltage is applied to an unselect common source line, an unselectbitline, an unselect sensing line, and an unselect wordline which arenot to connected to the selected memory cell CP, respectively. By doingso, data may be read.

Stored data may be erased by selecting predetermined memory cells CE.Memory cells selected in an erase operation may be memory cells sharinga selected wordline. Further, a sensing line is divided at respectivepredetermined memory cells to select memory cells sharing a sensing lineat an erase operation in the case where a plurality of sensing lines areopposite to one wordline.

A ground voltage is applied to a common source line CSL2, a selectbitline BL, and a select sensing line SL2 which are connected toselected memory cells CE, and an erase voltage is applied to a selectwordline WL2. Further, a ground voltage is applied to an unselect commonsource line, an unselect bitline, unselect sensing lines SL3 and SL4,and an unselect wordline which are not connected to selected memorycells. By doing so, selected memory cells may be erased at a time.

On the other hand, memory cells sharing a wordline, not a sensing line,with selected memory cells may inhibit an erase operation by applying anerase inhibit voltage. In other words, although an erase voltage isapplied to a select wordline, if a positive voltage, i.e., an eraseinhibit voltage is applied to an unselect sensing line opposite to awordline to which an erase voltage is applied, a voltage level of afloating gate rises to drop a voltage applied between a wordline and afloating gate. Thus, an electric field required for an erase operationis not established at the memory cell.

A table [TABLE 2] shows an operating voltage of a cell array accordingto an exemplary embodiment of the invention. In the table [TABLE 2],Vs11, Vs12, Vw11, Vw12, Vs1, Vs2, Vb11, and Vb12 denote a voltageapplied to a select sensing line, a voltage applied to an unselectsensing line, a voltage applied to a select wordline, a voltage appliedto an unselect wordline, a voltage applied to a select source line, avoltage applied to an unselect source line, a voltage applied to aselect bitline, and a voltage applied to an unselect bitline,respectively.

TABLE 2 Vsl1 Vsl2 Vwl1 Vwl2 Vs1 Vs2 Vbl1 Vbl2 program 8~10 V    0 V 2 V0 V 3.3 V   0 V 0 V 0 V read 1 V 0 V 1.5~2.0 V      0 V 0 V 0 V 1 V 0 Verase 0 V 3.3 V   10-12 V     0 V 0 V 0 V 0 V 0 V

The table [TABLE 2] is merely based on an exemplary embodiment of anoperation voltage of the cell array according to the present invention,and thus applied voltages may vary with structural characteristics of adevice.

An unselect wordline voltage Vs12 applied in an erase operation is aconstant voltage Vcc but may be replaced with an erase inhibit voltage.

FIG. 9A through FIG. 17A are top plan views for explaining a method forfabricating a non-volatile memory device according to an exemplaryembodiment of the present invention. FIG. 9B through FIG. 17B arecross-sectional views taken along lines II-II′ of FIG. 9A through FIG.17A, respectively. FIG. 9C through FIG. 17C are cross-sectional viewstaken along lines III-III′ of FIG. 9A through FIG. 17A, respectively.

Referring to FIG. 9A, FIG. 9B, and FIG. 9C, a device isolation layer 101is formed on a semiconductor substrate 100 to define a plurality ofactive regions. A gate insulation layer 102 is formed on the activeregion, and a floating gate conductive layer 104 is formed on an entiresurface of the substrate 100. The floating gate conductive layer 104 maybe made of polysilicon and become conductive by implanting impuritiesthereinto. A hard mask pattern 106 is formed on the floating gateconductive layer 104. The hard mask pattern 106 has a groove 108crossing over the active region and the device isolation layer 101 andexposing the floating gate conductive layer 104. Using the hard maskpattern 106 as an oxidation barrier layer, a sacrificial oxide pattern110 is formed to thermally oxidize the floating gate conductive layer104. The sacrificial oxide pattern 110 has an elliptical section.

Referring to FIG. 10A, FIG. 10B, and FIG. 10, the sacrificial oxidepattern 110 is removed to expose the floating gate conductive layer 104.A recess region 109 is formed at a portion where the sacrificial oxidepattern 110 is removed. A floating gate conductive layer 104 exposed inthe groove 108 is removed to form a removal region 112 where the deviceisolation layer 101 or the gate insulation layer formed on the deviceisolation layer is removed. For example, after forming a mask with anopening exposing a floating gate conductive layer 104 over the deviceisolation layer 101, the floating gate conductive layer 104 disposedthereover may be removed using the mask as an etch mask.

Referring to FIG. 11A, FIG. 11B, and FIG. 11C, a thermal oxidationprocess is carried out to form a thermal oxide layer 114 on a surface ofthe floating gate conductive layer 104 exposed in the groove 108. Duringthis process, surface defects of the floating gate conductive layer maybe cured. A spacer insulation layer 116 is formed on the entire surfaceof the substrate to be covered in the groove 108. The spacer insulationlayer 116 is made of a material having an etch selectivity with respectto the hard mask pattern 106.

Referring to FIG. 12A, FIG. 12B, and FIG. 12C, the spacer insulationlayer 116 is anisotropically etched to form a spacer insulation pattern116 a on a sidewall of the groove. An insulation pattern 116 b may beformed on a device isolation layer where the floating gate conductivelayer 104 is removed, covering the sidewall of the floating gateconductive layer 104. Not only the spacer insulation layer 116 but alsothe thermal oxide layer 114 on the floating gate conductive layer 104 isremoved to expose a floating gate conductive layer 104 between oppositespacer insulation patterns 116.

Referring to FIG. 13A, FIG. 13B, and FIG. 13C, the substrate is annealedto cure defects generated in an etch process of forming the spacerinsulation pattern 116. As a result, the floating gate conductive layer104 exposed between the spacer insulation patterns 116 may be thermallyoxidized to form a thermal oxide layer 115.

A dielectric layer 118 is formed on an entire surface of the substrate.A top gate conductive layer 120 is formed on the dielectric layer 118 tofill an area between the spacer insulation patterns 116. The dielectriclayer 118 may be made of metal oxide having a higher dielectric constantthan silicon oxide, and the top gate conductive layer 120 may be made ofdoped polysilicon. The top gate conductive layer 120 and the dielectriclayer 118 are planarized to expose the hard mask layer 106. Theplanarization of the top gate conductive layer 120 and the dielectriclayer 118 may be done using CMP or an anisotropic etchback. As a result,a conformal dielectric layer 118 is interposed between the spacerinsulation patterns 116 to fill the top gate conductive layer 120.

A capping layer 122 is formed on the top gate conductive layer 120. Thecapping layer 122 may be made of oxide having an etch selectivity withrespect to the hard mask layer 106 and the floating gate conductivelayer 104.

Referring to FIG. 14A, FIG. 14B, and FIG. 14C, the hard mask layer 106is removed to expose the floating gate conductive layer 104 andsidewalls of and the spacer insulation patterns 116. The floating gateconductive layer 104 is patterned to be self-aligned with the sidewallsof the spacer insulation patterns 116, forming a floating gate 104 a.The capping layer 122 on the top gate conductive layer 120 acts as anetch-stop layer while etching the hard mask layer 106 and the floatinggate conductive layer 104. As a result, floating gates 104 a are formedon the active region. The floating gates 104 a have sidewallsself-aligned with sidewalls of the spacer insulation patterns 116. Aspreviously described in FIG. 10A, FIG. 10B, and FIG. 10C, when asacrificial oxide pattern is formed on a floating gate and etched toform a recess region, a tip 104 t including a boundary portion of thesidewall of the floating gates 104 a and the recess region 109 may beformed at the edge of the floating gate 104 a.

Referring to FIG. 15A, FIG. 15B, and FIG. 15C, an oxide layer 124 isformed on a sidewall of the floating gate 104 a. The oxide layer 124 isconnected to an oxide layer below the spacer insulation pattern 116 tobe a tunnel oxide layer covering the tip 104 t. The oxide layer 124 maybe a thermal oxide layer where the sidewall of the floating gate 104 ais oxidized. A gate insulation layer 102 remaining at opposite sides ofthe floating gate 104 a may become thicker.

The oxide layer 124 may be formed after the sidewall of the spacerinsulation patterns 116 is partially etched isotropically.Alternatively, after the sidewall of the floating gate 104 a isthermally oxidized to cure etch damage, a thermal oxide layer isisotropically etched to form an additional thermal oxide layer or a CVDoxide layer. Thus, the oxide layer 124 is formed.

Referring to FIG. 16A, FIG. 16B, and FIG. 16C, a spacer conductive layeris formed on an entire surface of the substrate. The spacer conductivelayer is anisotropically etched to form conductive patterns 126 a and126 b on a sidewall including the spacer insulation pattern 116 a andthe floating gate 104 a. The conductive patterns 126 a and 126 b may besymmetrical with each other.

Referring to FIG. 17A, FIG. 17B, and FIG. 17C, using the structures onthe substrate as an ion implanting mask, impurities are implanted intothe active region. A source region 128 may be formed at an active regionbetween first conductive patterns 126 a, and a drain region 130 may beformed at an independent active region between second conductivepatterns 126 b.

As explained so far, a select gate electrode and a control gateelectrode are formed on a floating gate and a voltage is applied torespective gate electrodes to perform program and erase operations. Inthe program operation, a program voltage is applied to the select gateelectrode to inject charges from a channel. Therefore, a high voltage isnot applied to a source region or a drain region. As a result, a writeoperation is performed more stably than a split-gate memory device inwhich a high voltage is applied to a source region to perform a writeoperation. Since the gate electrode and the control gate electrode areformed on the floating gate, the cell area is further reduced than anEEPROM in which a control gate electrode is formed to be spaced apartfrom a floating gate and a stacked select gate electrode.

Having described the exemplary embodiments of the present invention, itis further noted that is readily apparent to those reasonably skilled inthe art that various modifications may be made without departing fromthe spirit and scope of the invention which is defined by the metes andbounds of the appended claims.

1. A non-volatile memory device comprising: a device isolation layerformed to define a plurality of active regions on a semiconductorsubstrate; a gate insulation layer formed on the respective activeregions; a floating gate formed on the respective gate insulationlayers; a sensing line formed on the gate insulation layer and thefloating gate to cross over the active regions; a wordline formed on asidewall of the floating gate and the gate insulation layer to crossover the active regions, the wordline being opposite to the sensingline, wherein the sensing line comprises a top sensing line crossingover the floating gate and a sidewall sensing line crossing over thesidewall of the floating gate and the gate insulation layer opposite tothe wordline; an intergate dielectric interposed between the sensingline and the floating gate; an intergate dielectric interposed betweenthe sensing line and the floating gate; a tunnel insulation layerinterposed between the wordline and the floating gate; and a spacerinsulation pattern interposed between the top sensing line and thesidewall sensing line and between the top sensing line and the wordline.2. The non-volatile memory device of claim 1, wherein a capacitancebetween the floating gate and the sensing line is higher than acapacitance between the floating gate and the wordline.
 3. Thenon-volatile memory device of claim 2, wherein the intergate dielectricincludes a material having a higher dielectric constant than the tunnelinsulation layer.
 4. The non-volatile memory device of claim 1, whereinthe sidewall sensing line and the wordline are symmetrical with eachother.
 5. The non-volatile memory device of claim 1, wherein theintergate dielectric between the top sensing line and the floating gateincludes a material having a higher dielectric constant than the tunnelinsulation layer.
 6. The non-volatile memory device of claim 5, whereinthe intergate dielectric between the sidewall sensing line and thefloating gate is made of the same material as the tunnel insulationlayer.
 7. The non-volatile memory device of claim 1, wherein thefloating gate has a tip formed toward the control gate electrode.
 8. Thenon-volatile memory device of claim 1, further comprising: a drainregion formed in respective active regions adjacent to the sensing line;and a common source line formed at an active region adjacent to thewordline to be connected to the wordline in parallel.
 9. Thenon-volatile memory device of claim 1, wherein the floating gate, thesensing line, and the wordline on the active region constitute a memorycell, and the sensing line is divided into predetermined memory cellunits to allow a plurality of sensing lines to corresponding torespective wordlines.